Former CFTC Commissioner Bart Chilton, who famously blasted high-frequency traders as "cheetahs" when he was a regulator, has gone to work with a leading high-frequency trading association, the group said Thursday.

The switch is a dramatic example of a regulator becoming a paid consultant for an industry he once criticized—and it says as much about how the high-frequency trading industry is changing its approach as it does about Washington's often-criticized revolving door.

Chilton, who left the CFTC earlier this year, joined the law and lobbying firm of DLA Piper as a senior policy advisor in April. On Thursday, the Modern Markets Initiative announced that Chilton and DLA Piper will work with the association's newly appointed CEO Bill Harts on "regulatory and public policy matters."

Adam Jeffery | CNBC

Former CFTC Commissioner Bart Chilton

"People are going to say, 'wait a minute, you used to beat the [stuff] out of those guys,' and I did, but I never said they should go away," Chilton said. Members of the Modern Markets Initiative, he said, "are the white hats among the HFTs. These guys are the first guys who want to be regulated and be part of the conversation."

With a shock of long white hair falling almost to his shoulders and an equally vibrant rhetoric, Chilton was among the most visible commissioners at the CFTC, which he joined after an appointment by President George W. Bush in 2007.

As early as 2010, Chilton began making speeches about high-frequency trading, raising questions about the role and safety of lightning quick, computer-driven trading strategies. That debate exploded onto the national scene earlier this year with the publication of Michael Lewis' book "Flash Boys," an extremely critical take on high-frequency trading.

Lewis said modern financial markets are so damaged by high-frequency trading strategies that they have been "rigged" by the industry. The burst of attention from the book has accelerated calls in Washington for new regulation of high-frequency trading practices.

Chilton said he has not changed his policy views on high-frequency trading, including that HFT needs to be regulated, that high-speed trading algorithms need "kill switches" in case of trouble, and other measures to keep trading fair and safe. He also said he expects the Modern Markets Initiative to roll out a series of policy recommendations later this year. He declined to reveal the fee the association is paying DLA Piper for its services.

Asked about the hiring, Modern Markets Initiative spokesman Kevin Madden said, "The MMI members welcome perspectives based on experience when it comes to countering many of the misperceptions folks have about HFT."

In a 2010 speech before the High Frequency Trading World USA conference, Chilton weighed into the debate for the first time: "HFT trading is part of our trading today, but should it remain the same?" he asked. "Is this type of trading outside of—or is it even inimical to—the fundamental purposes of capital formation and risk management in these markets?"

In a 2011 speech entitled "Caging the Financial Cheetahs," Chilton likened high-frequency traders to the fleet-footed felines of the African prairie. "If markets are going to be efficient and effective and less volatile, we need to cage the cheetahs," Chilton said at the time. "I'm not saying they should be extinct, and overly burdensome regulations shouldn't endanger them as a species, but they need to be confined."

Chilton's speeches generally focused on the need for regulation and fairness in high-frequency trading, not the elimination of it.

Today, Chilton says his policy views have remained consistent in his new role. "The HFT guys don't particularly like that I called them cheetahs, but at the same time, it's not inconsistent with the policy I've always espoused," he said. And Chilton added that he is prepared to register as a lobbyist if his new role meets the legal threshold for doing so.